In my last post, I referred to reference books on antique jewellery that I used the most. It turned out that all the books I mentioned are no longer in print so I said I would talk about books that are still in print in my next post. That proved to be more difficult than I thought it would be. So many of the books I have on antique necklaces, earrings and rings, and so on are out of print. So, searching Amazon and Book Depository to see what books were still available for sale, I located the following which I have found very useful.
Good overview of antique jewellery:

Understanding Jewellery, David Bennet and Daniela Mascetti (Amazon and Book Depository)
Good overview of Georgian jewellery:

Georgian Jewellery: 1714-1830, Ginny Redington Dawes and Olivia Collings (Amazon and Book Depository)
Victorian jewellery coverage, particularly everyday wear items of jewellery, made of materials such as such as agate, silver, tortoiseshell and jet:

Victorian Jewelry: Unexplored Treasures, Ginny Redington Dawes and Corinne Davidov (Amazon)
Mourning jewellery from the Georgian and Victorian periods:

Mourning Art and Jewelry, Maureen DeLorme (Book Depository and Amazon)
In Death Lamented: The Tradition of Anglo-American Mourning Jewelry, Sarah Nehama and Anne E. Bentley (Amazon)
Whitby Jet, Helen and Katy Muller (Book Depository and Amazon)
A great book on gemstones with beautiful pictures:

Gem: the Definitive Visual Guide, DK (Book Depository)